Thermostatic control device



Aug. 29, 1950 J. E. WOODS THERMOSTATIC CONTROL DEVICE Filed Feb. 7, 1948 UNIT 44 g COUPLING FIG.3

UNIT

44 g COUPLING ZZI JNVENTOR.

JOHN E. WOODS ATTORNEYS FIG. 2

Patented Aug. 29, 1950 2352 9 894 R itiios' rahio ooN'rieoiJ set/tee s, Cbhasset}! assigniii" to msfpii' Corporation; Boston, Mass; iii Delaware 1 Claim:

Th'eprseiit invention f't tb' mandate control devicesandi'n": paiticularly to then-j mostat'ic control devices for contrblliilg' the stem of an ante tive ran The conv j ream the crank shaft throiigli a belt been fbiiiid objectidriabl'e, since the fan abshrbs chm sidei'able ower the ighr steeds. high engine seeds, run spec eperatien er the rat is ii'ot hecess ry because of the" ra n effect of the vehicle r. It has 'eeeatiy been pr 1' V carthis between the engine and the co r pling being controlled thermostatically whereby the ran is' operated at low speed or cut off alto gether when the water is below a certain temperature and at higher speed as the water temiterat'ure rises. The eiectromagnetie "coupling may take any form such as a manganese-tea or similar system but preferably comprises a variableslip device including a rheostat which controlled by the thermostatic devices. The preferiedrheostat is a carbon pile device. Becaiise 'of me necessity "or apply s a pressure-to the pile, the bellows preferabl" has a vat-or fill 'ahd normally operates with substantial aresfsiiiw above atmosphere so t t adequate compressive force may be appl '"d' to the one. This ns thatif the bellows f leaks for any reason, the pressure is taken 'ofithe pileand the fan will fail to operate.

lonal netted of drivin the 7 The principal object of the present invention In the accompanying drawings Fig. 1 is a sectional elevation of the preferred system according to the present invention; Fig. 2 is a sectional elevation showing operation upon loss of liquid from the thermostatic system; and Fig. 3 is a detail view of the pile-supporting spring.

The construction shown in Fig. 1 comprises a bulb l0 and an .expansible chamber indicated as a bellows E2, the latter being enclosed in a metal casing 14. The tube It] is adapted to be clamped within some part of water circulating system of the vehicle, preferably within the lower hose connection indicated at US. A capillary tube I8 connects the bulb IS with the interior of the bellows [2. The bulb, tube and bellows are com- 2 liquid a negligible an and are at t e temperature ated. norexample, "er-amend ihi'xtuie "aif'i'n. 3 9 overly bellows as a thrust member 32 ms a biit'tb'n 34 on. the biit'td'h 34 is adapted, :1 expansion tithe bellow's, to engage the plunger 22 in the space be" tween the fingers "21 l w p [since the taper pressure of the an is small at non-operating emp l tures, the liquid serves a step to limit contraction of the bellows; Thus no mechanical internal stop is required. Therefore, under non-operating conditions, that is, when the met veh'l e is in operation, the bellws as'su'riles the position shown in 7 1g. 1, the batten 31': being then or contact with the pile. For reasons to be explained later, the length of the bellows in the non-operating condition of Fig. 1 is greater than the free length of the bellows; in other words, the bellows is initially filled with sufiicient liquid to expand it to a length somewhat greater than its free length.

In case of a leak which causes the liquid to drain out of the bellows, the present invention provides a fail-safe arrangement. To this end there is provided a third terminal 36 mounted on but insulated from the casing and having a direct wire connection 38 to the terminal 25. Extending inwardly from the terminal 35 is a bowed contact spring 49 which normally bears against the upper part of the bellows but is insulated therefrom by a pad 42. The spring 40 is free to follow the bellows upon an expansive movement, but if the liquid drains out of the bellows due to a leak, the bellows contracts to the free length position of Fig. 2, and the member 4|] does not follow it, whereby contact is then made between the spring 30 and the spring 4|]. This establishes a shunt around the resistor 20, by reason of the connection 38.

As shown in Fig. 1 the system includes a. coupling unit designated generally at 43. The crank shaft 44 of the engine is connected through the coupling unit to the fan shaft 45 to drive the fan 46. The coupling unit is here shown in purel diagrammatic form because it may comprise any type of device for variably driving the crank shaft. For example, it may comprise an electrical generator-motor unit, the motor speed being controlled by the resistor 20 in series with the armature. A simpler form of device is the usual electromagnetic slip coupling arrangement whereby as the fiux is varied by the change of current the fan shaft is more or less tightly coupled to the driving shaft 44. In any event, regardless of the exact form of the electromagnetic coupling, it will be understood that an irrcrease of pressure on the pile produces an increase in speed of the fan driven by the crank shaft.

In operation, as the engine is started up from its cold condition, the button 34 is out of contact with the diaphragm 24. The fan is then shut down. This makes for a quick rise in water temperature to the desired value. Up to about 150, the vapor pressure is negligible and the condition of the bellows is determined by the liquid fill. Since the change in volume of the liquid up to about 150 is relatively small, there is no substantial change in the bellows. As the temperature increases to a predetermined value, say 160, the expansion of the bellows brings the button 34 into contact with the plunger 22. As the temperature increases, the further expansion of the bellows effects further compression of the pile, so that minimum resistance is preferably reached at about 175.

At sustained high engine speed where the ram eifect is adequate to provide substantial cooling, the water temperature tends to drop, thereby relieving the pressure on the carbon pile and thus diminishing the fan speed or even cutting out the fan altogether. It will be noted that in the condition of Fig. 1 and as heretofore stated, the bellows length is somewhat greater than its free length but it is prevented from collapsing to its free length by the liquid fill.

In the event of a leak the bellows contracts to its free length as shown in Fig. 2, thereby allowing the spring 30 to engage the contact 40 and establish the short-circuit connection 38 4 around the resistor. This causes the fan to operate at full speed. This is the fail-safe condit'ion, which insures full speed fan operation and prevents overheating of the engine in the event of bellows failure.

It will be understood that the invention is not limited to the particular elements herein shown, but may employ other forms. For example, the bellows I2 is representative of expansible chambers, which may take other forms such as diaphragms, capsules and the like, and the carbon pile resistor is representative of pressure-responsive circuit control devices as will be understood by those skilled in the art.

Having thus described the invention, I claim:

In a thermostatic control system for an automotive fan, a thermostat to be responsive to the temperature of the circulating water including a bellows filled with liquid to hold the bellows normally at a length greater than its free length, a pressure-responsive variable resistor actuated by expansion of the bellows due to vapor pressure, a spring member pressing against the bellows, a contact member normally bearing against but insulated from the bellows and normally out of contact with the spring member, the contact member being out of engagement with the bellows if the bellows collapses to its free length due to loss of liquid, whereby said spring member then engages said contact member, and a shunt for the resistor established by the engagement of said spring and contact members.

JOHN E. WOODS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 7 Date 

